Knee Prosthesis

ABSTRACT

A knee joint prosthesis assembly can include a femoral component that has a medial and a lateral condyle portion connected by a patellar track portion. The femoral component can form an opening between the medial and lateral condyles. A tibial component can have a medial portion that includes a first engagement structure and a lateral portion that includes a second engagement structure. A medial bearing can have a third engagement structure formed thereon that selectively engages the first engagement structure. A lateral bearing separately formed and independent from the medial bearing can have a fourth engagement structure formed thereon that selectively engages the second engagement structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit and priority of 61/181,938, filedMay 28, 2009. The entire disclosure of the above application areincorporated herein by reference.

FIELD

The present disclosure relates to a knee joint prosthesis including atibial tray component having independent and selectively attachablebearings including fixed and mobile bearings that can be secured tomedial and lateral sides of the tibial tray according to the needs of aparticular patient.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

A knee joint prosthesis can generally comprise a femoral component and atibial component. The femoral component and the tibial component can bedesigned to be surgically attached to the distal end of the femur andthe proximal end of the tibia, respectively. The femoral component canfurther be designed to cooperate with the tibial component in simulatingthe articulating motion of an anatomical knee joint. In many examples,the tibial component can further include a bearing component thatincludes articulation surfaces on the medial and lateral side forcooperating with a medial and lateral condyle portion of the femoralcomponent. In some examples, the bearing component can be fixed relativeto the tibial component. In other examples, the bearing component can bea mobile bearing component that has at least a portion that can moverelative to the tibial component during articulation of the femoralcomponent.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

A knee joint prosthesis assembly can include a femoral component thathas a medial and a lateral condyle portion connected by a patellar trackportion. The femoral component can form an opening between the medialand lateral condyles. A tibial component can have a medial portion thatincludes a first engagement structure and a lateral portion thatincludes a second engagement structure. A medial bearing can have athird engagement structure formed thereon that selectively engages thefirst engagement structure. A lateral bearing separately formed andindependent from the medial bearing can have a fourth engagementstructure formed thereon that selectively engages the second engagementstructure.

According to additional features, the medial and lateral condyles of thefemoral component can be configured to articulate along complementarybearing surfaces of the medial and lateral bearings. The medial andlateral bearings can both be configured to be fixed relative to thetibial component. According to other features, one of the medial andlateral bearings can be fixed relative to the tibial component and theother of the medial and lateral bearings can be a mobile bearingcomponent. In other configurations, both of the medial and lateralbearings can be mobile bearing components that have respective portionsthat slidably advance along an opposing surface of the tibial component.One of the medial and lateral condyle portions that articulates on themobile bearing component can have a spherical, convex articulationssurface.

According to other features, the mobile bearing component can include afixed portion that has the third or fourth engagement structure that isconfigured to statically engage the tibial component and a mobilebearing portion that is configured to slidably advance along theopposing surface of the tibial component. The fixed portion can define apocket that receives and confines the mobile bearing portiontherewithin. The mobile bearing portion can be formed of a polymericmaterial and can include a metallic layer of material disposed around aperimeter thereof. A locking bar can be provided that selectivelylocates between the tibial component and the medial and lateralbearings. The locking bar can cooperate with the first, second, thirdand fourth engagement structures and can secure the medial and lateralbearings to the tibial component.

A method of implanting a knee prosthesis can include providing a kit oftibial trays, medial bearings and lateral bearings. The tibial trays caninclude a bicruciate retaining tray and a posterior cruciate retainingtray. The medial and lateral bearings can include a plurality of fixedand mobile medial and lateral bearings. The patient's proximal tibia anddistal femur can be accessed. The proximal and distal femur and at leastone of an anterior cruciate ligament and posterior cruciate ligament canbe assessed. A bicruciate retaining or posterior cruciate retainingtibial tray can be selected from the kit based on the assessing. Theselected tibial tray can be secured to the proximal tibia. Thedesirability of a fixed or mobile bearing can be determined for themedial and lateral sides of the selected tibial tray based on theassessing. The medial and lateral bearings can be intraoperatively andindependently selected from the kit. The selected medial and lateralbearings can be secured to the selected tibial tray.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is an anterior perspective view of a knee prosthesis assemblyaccording to one example of the present teachings;

FIG. 2 is a posterior perspective view of the knee prosthesis of FIG. 1;

FIG. 3 is a lateral perspective view of a femoral component of the kneeprosthesis of FIG. 1;

FIG. 4 is a superior perspective view of a tibial tray of the kneeprosthesis of FIG. 1;

FIG. 5 is an inferior perspective view of the tibial tray of FIG. 4;

FIG. 6 is a perspective view of a mobile bearing of the knee prosthesisof FIG. 1;

FIG. 7 is a perspective view of a fixed bearing of the knee prosthesisof FIG. 1;

FIG. 8 is a perspective view of a locking bar associated with the fixedbearing of a knee prosthesis of FIG. 1;

FIG. 9 is a partially exploded posterior view of a knee prosthesisconstructed in accordance to additional features of the presentteachings;

FIG. 10 is a posterior perspective view of the knee prosthesis of FIG.9;

FIG. 11 is an anterior perspective view of a tibial tray and fixedbearing portion of the knee prosthesis of FIG. 10;

FIG. 12 is a perspective view of a mobile bearing that slidablycooperates within a pocket formed on the fixed bearing of FIG. 11;

FIG. 13 is an anterior perspective view of a knee prosthesis assemblyaccording to another example of the present teachings that incorporatesa mobile bearing component that is selectively attachable to a medialside of a tibial tray and a fixed bearing component that is selectivelyattachable to a lateral side of the tibial tray;

FIG. 14 is an anterior superior exploded perspective view of the kneeprosthesis assembly of FIG. 13;

FIG. 15 is an anterior inferior exploded perspective view of the kneeprosthesis assembly of FIG. 13;

FIG. 16 is a perspective view of a mobile bearing incorporating a metalsleeve according to various features;

FIG. 17 is an anterior perspective view of a tibial tray constructed inaccordance to additional features and incorporating a pair of fixedbearings that are selectively locked to the tibial tray with a lockingbar;

FIG. 18 is an anterior superior exploded perspective view of the tibialtray assembly of FIG. 17;

FIG. 19 is an anterior inferior exploded perspective view of the tibialtray assembly of FIG. 17;

FIG. 20 is an anterior perspective view of a tibial tray constructed inaccordance to additional features of the present teachings; and

FIG. 21 is a kit having a plurality of tibial trays, medial bearings andlateral bearings according to the present teachings.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

With initial reference to FIGS. 1 and 2, a knee prosthesis assemblyconstructed in accordance to one example of the present teachings isshown and generally identified at reference numeral 10. The kneeprosthesis assembly 10 can generally include a femoral component 12, atibial tray 14, a medial floating or mobile bearing 16 and a lateralfixed bearing 18. As will be described, the knee prosthesis assembly 10can be used when it is desirable to retain or reconstruct an anteriorcruciate ligament (ACL) and/or a posterior cruciate ligament (PCL).

The respective components of the knee prosthesis assembly 10 can bepatient specific, such that each component can be constructed foroptimal features for a given patient. For example, the bone interfacemargins of the femoral component 12 and tibial tray 14 can be patientspecific for optimized bone coverage. In addition, the overall size,such as anterior-posterior dimensions and bone cut geometry can bedetermined and used for manufacturing the components of the kneeprosthesis assembly 10. Moreover, some articulation features can bedetermined and used as criteria for forming the components of the kneeprosthesis assembly 10. In sum, each of the components of the kneeprosthesis assembly 10 can be a patient-specific implant, a semi-customimplant or an off-the-shelf or standard production implant. Acustom-made implant is a patient-specific, one-of-a-kind implantspecifically made for a particular patient, and consequently there is noinventory associated with such implant. Standard or off-the shelfimplants are available and stocked in a number of sizes, typically sixor more, and a number of configurations or types, including bilateral orunilateral implants, constrained, semi-constrained, mobile, etc. Becauseof the variety of sizes and configurations that are kept in stock to beaccommodated by different patients, a large inventory of standardimplants is created, and several molds for each type and size of implantmay be used. Semi-custom implants can provide an intermediate solutionbetween custom-made and off-the-shelf implants. Semi-custom implantsreduce the size of inventory and molds required for production, whileallowing some degree of patient-specific customization. Additionaldescription of patient-specific implants and semi-custom implants andtheir implementations may be found in copending patent application Ser.No. 12/103,824, filed Apr. 16, 2008 and entitled: Method and Apparatusfor Manufacturing an Implant, the disclosure of which is herebyincorporated by reference.

With additional reference to FIG. 3, the femoral component 12 will nowbe described in greater detail. The femoral component 12 can generallycomprise a cruciate retaining prosthesis and includes various portionsto replace or mimic the distal femur. The femoral component 12 caninclude a medial condyle portion 20 and a lateral condyle portion 22.The condyle portions 20 and 22 can replace the medial and lateralcondyles of a distal femur. The medial and lateral condyle portions 20and 22 can interconnect and be formed as a single piece with a patellartrack portion 26. The patellar track portion 26 can allow forarticulation of a patella, either natural or prosthetic patella, oncethe femoral component 12 is implanted onto the distal femur. The medialand lateral condyle portions 20 and 22 and the patellar track portion 26can generally define an exterior portion of the femoral component 12.The femoral component 12 can define an opening or passage 30 between themedial and lateral condyle portions 20 and 22. As can be appreciated,the passage 30 can accommodate, and provide clearance for a host ACLand/or PCL or a reconstructed ACL and/or PCL. The medial condyle portion20 can include a spherical contact surface that is convex in ananterior/posterior direction and a medial/lateral direction.

The femoral component 12 can include a bone contacting or inferiorsurface 34 (FIG. 2). The inferior surface 34 can include an anteriorsurface 36 that can be substantially flat and formed generally parallelto a pair of posterior surfaces 38 a and 38 b. A pair of intermediatesurfaces 40 a and 40 b are provided generally at an intermediate portionof the inferior surface 34. A pair of angled anterior transitionsurfaces 42 a and 42 b generally connect the anterior surface 36 withthe intermediate surfaces 40 a and 40 b. Similarly, a pair of angledposterior transition surfaces 44 a and 44 b are provided between therespective posterior surfaces 38 a and 38 b and the intermediatesurfaces 40 a and 40 b. In one example, a threaded boss 50 a and 50 bcan be provided on each of the intermediate surfaces 40 a and 40 b,respectively. Similarly, a threaded boss 52 a and 52 b can be providedon the posterior surfaces 38 a and 38 b, respectively. The bosses 50 a,50 b, 52 a and 52 b can be optionally used to threadably couple withvarious augments (not specifically shown) as necessary. The femoralcomponent 12 can be formed as a unitary structure and cast of abiocompatible high strength alloy, such as cobalt-chromium-molybdenumalloy or similar suitable material. All surfaces, which do not contactthe femur, can be highly polished to provide smooth articulating bearingsurfaces. The interior surface 34 of the femoral component 12 can beroughened or uneven or include porous material to allow bone ingrowth orattachment with bone cement. Other features of the femoral component 10can include those associated with the Oxford® Partial Knee marketed byBiomet, Inc.

With reference now to FIGS. 1, 2, 4 and 5, the tibial tray 14 will nowbe described in greater detail. The tibial tray 14 can include agenerally U-shaped body having a medial portion 60 and a lateral portion62. A slot 64 can be formed in the tibial tray 14 generally between themedial and lateral portion 60 and 62. As with the passage 30 of thefemoral component, the slot 64 of the tibial tray 14 can accommodate andprovide a clearance for a host ACL and/or PCL or a reconstructed ACLand/or PCL. During implantation, the tibial tray 14 can be advancedposteriorly, such that the slot 64 can accommodate a host ACL and/orPCL. In instances where a reconstructed ACL and/or PCL is used, a tray(and bearing) having a passage can be utilized. One suitableconfiguration is further described in commonly owned in U.S. Pat. No.7,255,715; issued Aug. 14, 2007 and is hereby incorporated by reference.The tibial tray 14 can include an inferior bone engaging side 66 (FIG.5) and a superior bearing engaging side 68 (FIG. 4). The medial portion60 of the superior bearing engaging side 68 can include a highlypolished tibial bearing surface 70. A rail 72 can extend in a generallyanterior/posterior direction adjacent to the highly polished tibialbearing surface 70. The lateral portion 62 can include engagingstructure 78 provided on the superior bearing engaging side 68. Theengaging structure 78 can include a pair of posts 80 and 82 integrallyformed at an anterior edge thereof. A retaining rail 84 can extendsuperiorly from a posterior edge of the lateral portion 62. The posts 80and 82 can both have an anterior groove 86 and a posterior groove 88,respectively. The retaining rail 84 can have a transverse groove 90formed on an inwardly facing surface. The tibial tray 14 can begenerally manufactured of cobalt-chromium-molybdenum alloy or othersuitable biocompatible material. A pair of fins 94 can extend from theinferior bone engaging side 66. While fins 94 are shown operativelyassociated with the tibial tray 14, other structures suitable forengaging a proximal tibia can include pegs, posts or porous material canadditionally or alternatively be provided on the inferior bone engagingside 66.

With reference to FIGS. 1, 2 and 6, the medial floating bearing 16 willnow be described in greater detail. The medial floating bearing 16 has asubstantially planar inferior bearing surface 100 which slidably movesand articulates relative to the highly polished tibial bearing surface70. The medial floating bearing 16 further includes a first bearingsurface 102. The first bearing surface 102 articulates with the medialcondyle portion 20 of the femoral component 12. The medial floatingbearing 16 can be formed from a surgical grade, low friction, and lowwearing plastic, such as ultra high molecular weight polyethylene(UHMWPE) or other suitable material.

With reference to FIGS. 1, 2 and 7, the lateral fixed bearing 18 caninclude engaging structure 106 formed on an inferior surface forcoupling with the engaging structure 78 provided on the lateral portion62 of the tibial tray 14. The engaging structure 106 can generallyinclude a posteriorly extending lip 110 and an anterior groove 112. Alocking bar 114 (FIG. 8) can be slidably inserted through the anteriorgroove 112 to interlock between the respective grooves 86 to capture thelateral fixed bearing 18 to the lateral portion 62 of the tibial tray14. The posteriorly extending lip 110 can be nestingly received by theretaining rail 84. The lateral fixed bearing 18 can include a secondbearing surface 120. The second bearing surface 120 can articulate withthe lateral condyle portion 22 of the femoral component 12. The lateralfixed bearing 18 can be formed from a surgical grade, low friction andlow wearing plastic, such as UHMWPE or other suitable material.

During use, the medial and lateral condyle portions 20 and 22 of thefemoral component 12 can articulate on the first and second bearingsurfaces 102 and 120 of the respective medial floating bearing 16 andlateral fixed bearing 18. As can be appreciated, the lateral fixedbearing 18 is static relative to the tibial tray 14 during articulationof the femoral component 12. The medial floating bearing 16 is free toslide along the highly polished tibial bearing surface 70 of the medialportion 60 of the tibial tray 14. The medial floating bearing 16 isbound on an inboard side by the rail 72.

While the embodiment shown in the figures includes a floating bearingprovided on a medial side and a fixed bearing provided on a lateralside, the location of these bearings can be swapped. Similarly, both ofthe medial and lateral sides can be formed with floating bearings orfixed bearings. Turning now to FIGS. 9-11, a knee prosthesis assemblyconstructed in accordance to additional features of the presentteachings is shown and generally identified at reference numeral 210.The knee prosthesis assembly 210 can generally include a femoralcomponent 212, a tibial tray 214, a medial side having a mobile bearingcomponent 216 and a lateral side having a fixed bearing 220. The mobilebearing component has a fixed portion 217 and a mobile bearing portion218. The femoral component 212 can be constructed similar to the femoralcomponent 12 described below. The fixed bearing 220 can be constructedsimilar to the lateral fixed bearing 18 described above. The mobilebearing component 216 can provide articulation that is fully conformingwith the femoral component 212. The mobile bearing portion 218 can becaptured around its perimeter by a pocket 222 formed by the fixedportion 217. In this way, the mobile bearing portion 218 can have areduced likelihood of becoming dislocated relative to the fixed portion217. While the mobile bearing component 216 is shown generallyassociated with the lateral side of the tibial tray 214, such aconfiguration can be additionally or alternatively provided on themedial portion of the tibial tray 214. In one example, the mobilebearing portion 218 can be formed by polyethylene orpolyetheretherketone (PEEK). As shown in FIG. 11, the fixed portion 217can have a pair of channels 226 formed thereon for guiding tabs 230provided on the mobile bearing portion 218 (FIG. 12). It will beappreciated that while the mobile bearing component 216 has beendescribed and shown incorporated on a medial portion of the tibial tray214, it can additionally or alternatively be incorporated on a lateralportion of the tibial tray 214. Likewise, while the fixed bearing 220has been described and shown incorporated on a lateral portion of thetibial tray 214, it can additionally or alternatively be incorporated ona medial portion of the tibial tray 214.

With reference now to FIGS. 13-16, a knee prosthesis assembly 310constructed in accordance to additional features of the presentteachings will be described. As with the other knee prosthesisassemblies disclosed herein, the knee prosthesis assembly 310 can bepatient specific, such that each component can be constructed foroptimal features for a given patient. In this regard, the kneeprosthesis assembly 310 can generally include the femoral component 12,a tibial tray 314, a mobile bearing component 316 and a fixed bearingcomponent 318. As shown, the mobile bearing component 316 is selectivelysecured to a medial portion 320 of the tibial tray 314 and a fixedbearing component 318 selectively secured to a lateral portion 322 ofthe tibial tray 314 for a left knee. However, it will be appreciated bythose skilled in the art that a mobile bearing component 316 can beprovided for both the medial portion 320 and the lateral portion 322 ofthe tibial tray 314. Similarly, a fixed bearing component 318 can beprovided for both of the medial portion 320 and the lateral portion 322of the tibial tray 314. Likewise, the fixed bearing component 318 canalternatively be provided only on the medial portion 320, while a medialbearing component 316 can be provided only on a lateral portion 322 ofthe tibial tray 314. In sum, any combination of mobile and fixed bearingcomponents can be available and selectively secured to either of themedial or lateral portions 320 and 322 of the tibial tray 314.

The femoral component 12 can be generally formed similar to the femoralcomponent 12 described in detail above. Again, the medial condyleportion 20 can have a spherical, convex articulation surface that cancooperate with the mobile bearing components 316 as will be describedherein. It is appreciated that a similar spherical, convex articulationsurface can be provided on the lateral condyle portion 22 in the eventthat a mobile bearing component is desired on the lateral portion 322 ofthe tibial tray 314.

The mobile bearing component 316 can generally include a fixed portion330 and a mobile bearing portion 332 (FIG. 14). The fixed portion 330can generally include a pocket 334 defined within a surrounding wall336. A superior surface 338 can be contoured to cooperate with theprofile of the medial condyle portion 20 of the femoral component 12. Aninferior surface 340 (FIG. 15) can have a channel 342 that tapersgenerally anteriorly for locking with a portion of the tibial tray 314as further discussed herein. A rail 346 can be formed into thesurrounding wall 336. A groove 348 can be formed around a posterior edgeof the fixed portion 330. The fixed portion 330 can have an inner wall349 that cooperates with the U-shaped profile of the tibial tray 314 toaccommodate a host or reconstructed ACL.

The mobile bearing portion 332 can have an outer perimeter surface 350that substantially matches a profile of the surrounding wall 336,however, is reduced in size so as to be stepped inwardly relative to thesurrounding wall 336 (see also FIG. 9) to allow movement within thesurrounding wall 336. Tabs 352 can extend in generally the medial andlateral directions from an inferior surface 354 of the mobile bearingportion 332. A superior articulating surface 358 can substantiallyconform to the profile of the medial condyle portion 20 of the femoralcomponent 12. The fixed portion 330 and the mobile bearing portion 332can be formed of UHMWPE or PEEK. According to additional features, amobile bearing portion 332′ (FIG. 16) can have a metal layer or band 359disposed around a perimeter. The metal layer 359 can precludepolymer-polymer contact between the perimeter of the mobile bearingportion 332′ and the surrounding wall 336 of the fixed portion 330 toinhibit wear. As shown in FIG. 16, similar features are identified withcommon reference numerals having a “prime” suffix.

The fixed bearing component 318 can generally include a superior surface360 that substantially conforms to and provides a surface contact withthe profile of the lateral condyle portion 22 of the femoral component12. A channel 362 can be formed along an anterior inferior surface 364and that generally tapers anteriorly. A groove 368 can be formed arounda posterior edge of the fixed bearing component 318. The fixed bearingcomponent 318 can have an inner wall 369 that cooperates with theU-shaped profile of the tibial tray 314 to accommodate a host orreconstructed ACL.

The tibial tray 314 can generally include a locating tab 370 formed onan anterior edge of the medial portion 320 and a locating tab 372 formedon an anterior edge of the lateral portion 322. A slot 374 can bedefined through the tibial tray 314 between the medial and lateralportions 320 and 322. The slot 374 can be configured to accommodate andprovide clearance for a host ACL and/or PCL or a reconstructed ACLand/or PCL. A retaining rail 375 can be formed around a posterior edgeof the medial portion 320. The retaining rail 375 can include a lip 376and a groove 378. A retaining rail 380 can be formed around a posterioredge of the lateral portion 322 of the tibial tray 314. The retainingrail 380 can generally include a lip 382 and a groove 384. An inferiorsurface 386 of the tibial tray 314 can be generally smooth, but may alsoincorporate a series of round grooved pegs. The inferior surface 386 canbe configured to be cemented or press-fit onto the proximal tibia. Thetibial tray 314 can be generally manufactured ofcobalt-chromium-molybdenum alloy or other suitable biocompatiblematerials.

Attaching the mobile bearing component 316 to the medial portion 320 ofthe tibial tray 314 will now be described according to one example. Atthe outset, the surgeon can select a given medial bearing component 316from a plurality of medial bearing components (see also kit 600, FIG.21) that satisfies the desired characteristics for a given patient, suchas height, articulation, etc. The mobile bearing portion 332 can beinitially advanced into the pocket 334 superiorly, such that the tabs352 can generally locate against the rail 346 formed on the fixedportion 330. Concurrently or subsequently, the fixed portion 330 can belocated onto the medial portion 320 of the tibial tray 314 along withthe mobile bearing portion 332 in an assembly. Next, a surgeon canslidably advance the mobile bearing component 316 in a directlygenerally posteriorly such that the channel 342 is progressivelyadvanced around the locating tab 370 and the groove 348 of the fixedportion 330 is located under the lip 376 of the retaining rail 375 onthe tibial tray 314. It will be appreciated that at this point, thefixed portion 330 remains static relative to the medial portion 320 ofthe tibial tray 314 while the mobile bearing portion 332 is free toslidably advance around the medial portion 320 of the tibial tray 314within the confines of the surrounding wall 336 of the pocket 334. Itcan be appreciated that articulation of the medial condyle portion 20 ofthe femoral component on the superior articulating surface 358 of themobile bearing portion 332 can influence the mobile bearing portion 332to rotate and/or slidably advance such as in an anterior/posteriordirection along the medial portion 320 around the pocket 334.

Connection of the fixed bearing component 318 to the lateral portion 322of the tibial tray 314 is similarly carried out. Initially, the inferiorsurface 364 of the fixed bearing component 318 is located onto thelateral portion 322 of the tibial tray 314. Next, the fixed bearingcomponent 318 is slidably advanced posteriorly, such that the channel362 slidably accommodates the locating tab 372 while the groove 368locates under the lip 380. The fixed bearing component 318 is adapted tobe statically secured relative to the lateral portion 322 of the tibialtray when assembled.

With reference now to FIGS. 17-19, a tibial tray assembly 413constructed in accordance to additional features of the presentteachings will be described. As with the other knee prosthesisassemblies disclosed herein, the tibial tray assembly 413 can be patientspecific, such that each component can be constructed for optimalfeatures for a given patient. In this regard, the tibial tray assembly413 can include a tibial tray 414, a first bearing component 416, asecond bearing component 418 and a locking bar 420. As with the tibialtray 314 described above, the tibial tray 414 can be generally U-shapedand provides a slot 422 that can be configured to accommodate andprovide clearance for a host ACL and/or PCL or a reconstructed ACLand/or PCL. Other examples of attaching an artificial or natural ACLand/or PCL may be found in “Knee Prosthesis Assembly with Ligament Link”Ser. No. (Attorney Docket No. 5490-000809 and 5490-000809/US/01), filedconcurrently herewith. As with the other bearing components disclosedherein, the first bearing component 416 and the second bearing component418 are both independently formed and intraoperatively selectedaccording to the needs of a given patient. The first bearing component416 and the second bearing component 418 are generally fixed bearingcomponents, however, a mobile bearing component may be similarlyprovided for either of the medial and/or lateral sides. As will becomeappreciated from the following discussion, the locking bar 420 can beused to selectively and intraoperatively secure the respective first andsecond bearing components 416 and 418 to the tibial tray 414. The firstbearing component 416 can have a superior surface 424, an inferiorsurface 426 (FIG. 19) having engagement grooves 427 and an anteriorchannel 428. Similarly, the second bearing component 418 can include asuperior surface 430, an inferior surface 432 (FIG. 19) havingengagement grooves 433 and an anterior channel 434.

The tibial tray 414 can include a medial portion 436, a lateral portion438, posterior engagement tabs 440, an anterior engagement bridge 442and anterior engagement tabs 443. The anterior engagement bridge 442 caninclude a track 444 formed thereon. The anterior engagement bridge 442can provide an increased thickness to the tibial tray 414 at theconnection between the medial and lateral portion 436 and 438,respectively to increase durability. A wall 446 can be formed on theanterior engagement bridge 442 adjacent to the track 444. The tibialtray 414 can have inferiorly extending posts 450.

The locking bar 420 can generally include a body 454 having a finger 456extending therefrom. A catch 458 can be formed on a terminal end of thefinger 456. The locking bar 420 can be formed of biocompatible metallicmaterial, such as titanium for example. The body 454 can further includea leading end 460 and a trailing end 462.

Attaching the respective first and second bearing components 416 and 418to the tibial tray 414 according to one example of the present teachingswill now be described. Once a surgeon has selected a first and secondbearing component 416 and 418 that satisfies the given needs of aparticular patient (see also kit 600, FIG. 21), they are independentlylocated onto the medial and lateral portions 436 and 438 of the tibialtray 414. In this regard, the posterior engagement tabs 440 of thetibial tray 414 can locate into the respective engagement grooves 427and 433 of the first and second bearing components 416 and 418. In someexamples, the respective first and second bearing components 416 and 418may be advanced posteriorly, such that the engagement tabs 440 can lockinto the engagement grooves 427 and 433. Concurrently, the anterior tabs443 can locate into the anterior engagement grooves 427 and 433 of thefirst and second bearing components 416 and 418. Next, a surgeon canslidably advance the leading end 460 of the locking bar 420 through therespective anterior channels 428 and 434 of the first and second bearingcomponents 416 and 418. Concurrently, a portion of the body 454 canlocate along a posterior side of the anterior engagement bridge 442while the finger 456 locates around an anterior side of the anteriorengagement bridge 442. The locking bar 420 can be further advanced untilthe catch 458 on the finger 456 can locate around the wall 446 on theanterior engagement bridge 442.

With reference now to FIG. 20, another tibial tray 514 constructed inaccordance to the present teachings is shown. The tibial tray 514generally includes an inferiorly extending stem 516. The tibial tray 514can be a full tibial tray that can be particularly suited for exampleswhere a central slot (such as the slot 422) for accommodating an ACL isnot needed. The tibial tray 514 includes posterior engagement tabs 540and an anterior engagement bridge 542. Anterior locating tabs 543 can beformed on the tray 514. The anterior engagement bridge 542 can include atrack 544. The tibial tray 514 can be configured to selectively andintraoperatively secure independent medial and lateral bearings, such asthe bearings 416 and 418 disclosed herein.

Turning now to FIG. 21, a kit 600 is shown having a collection of medialand lateral bearings that provide unique articulations, sizes andthicknesses (i.e., D1, D2, D3, etc.) and incorporate either a fixed ormobile configuration on the lateral and medial sides. The kit 600further includes the bicruciate retaining tibial tray and the posteriorcruciate retaining tray. As disclosed herein, the kit can beparticularly suited for allowing a surgeon the opportunity tointraoperatively select a given medial and/or lateral bearing componentand tibial tray that is particularly suited for a given patient. It iscontemplated that with the kit 600, a surgeon can also utilize thecomponents during a revision surgery where the level of constraint needsto be increased. In this regard, a surgeon may only desire to changesome components while leaving others unchanged.

As used herein, the terms superior, superiorly, superior direction areused to generally refer to the anatomical meaning, such as higher inplace or position or generally situated above. Similarly, the termsinferior, inferiorly, inferior direction are used to generally refer tothe anatomical meaning, such as lower in place or position or generallysituated below.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

1. A knee joint prosthesis assembly comprising: a femoral componenthaving a medial and a lateral condyle portion connected by a patellartrack portion, the femoral component forming an opening between themedial and lateral condyles; a unitary tibial component having a medialportion that includes a first engagement structure and a lateral portionthat includes a second engagement structure; a medial bearing having athird engagement structure formed thereon that selectively engages thefirst engagement structure; and a lateral bearing separately formed andindependent from the medial bearing and having a fourth engagementstructure formed thereon that selectively engages the second engagementstructure.
 2. The knee joint prosthesis of claim 1 wherein the medialand lateral condyles of the femoral component are configured toarticulate along complementary bearing surfaces of the medial andlateral bearings.
 3. The knee joint prosthesis of claim 2 wherein themedial and lateral bearings are both configured to be fixed relative tothe tibial component.
 4. The knee joint prosthesis of claim 2 whereinone of the medial and lateral bearings is fixed relative to the tibialcomponent and the other of the medial and lateral bearings is a mobilebearing component wherein at least a portion of the mobile bearing isconfigured to slidably advance along an opposing surface of the tibialcomponent.
 5. The knee joint prosthesis of claim 2 wherein both of themedial and lateral bearings are mobile bearing components that haverespective portions that slidably advance along an opposing surface ofthe tibial component.
 6. The knee joint prosthesis of claim 4 wherein acondyle portion of the medial and lateral condyle portions thatarticulates on the mobile bearing component has a spherical, convexarticulation surface.
 7. The knee joint prosthesis of claim 4 whereinthe mobile bearing component includes a fixed portion having the thirdor fourth engagement structure that is configured to statically engagethe tibial component and a mobile bearing portion that is configured toslidably advance along the opposing surface of the tibial component. 8.The knee joint prosthesis of claim 7 wherein the fixed portion defines apocket that receives and confines the mobile bearing portiontherewithin.
 9. The knee joint prosthesis of claim 8 wherein the mobilebearing portion is formed of a polymeric material and includes ametallic layer of material disposed around a perimeter thereof.
 10. Theknee joint prosthesis of claim 1, further comprising: a locking bar thatselectively locates between the tibial component and the medial andlateral bearings, the locking bar cooperating with the first, second,third and fourth engagement structures and securing the medial andlateral bearings to the tibial component.
 11. The knee joint prosthesisof claim 1 wherein the tibial component is U-shaped and is adapted toaccommodate an anterior cruciate ligament.
 12. The knee joint prosthesisof claim 1 wherein the tibial component has an inferiorly extendingstem.
 13. The knee joint prosthesis of claim 1, further comprising aplurality of fixed and mobile medial bearings and a plurality ofseparate fixed and mobile lateral bearings, wherein the plurality ofmedial and lateral bearings have distinct thicknesses in asuperior/inferior direction.
 14. A method of implanting a kneeprosthesis, the method comprising: providing a kit of tibial trays,medial bearings and lateral bearings, the tibial trays including abicruciate retaining tray and a posterior cruciate retaining tray, themedial and lateral bearings including a plurality of fixed and mobilemedial and lateral bearings; accessing a patient's proximal tibia anddistal femur; assessing the proximal and distal femur and at least oneof an anterior cruciate ligament and posterior cruciate ligament;selecting one of a bicruciate retaining or posterior cruciate retainingtibial tray from the kit based on the assessing; securing the selectedtibial tray to the proximal tibia; determining whether a fixed or mobilebearing is desired for a medial and lateral side of the selected tibialtray based on the assessing; intraoperatively and independentlyselecting a medial and a lateral bearing from the kit of bearings; andsecuring the selected medial and lateral bearings to the selected tibialtray.
 15. The method of claim 14 wherein selecting the tibial traycomprises selecting the bicruciate retaining tray having a U-shaped slotand wherein securing the bicruciate tibial tray comprises locating ananterior cruciate ligament through the U-shaped slot.
 16. The method ofclaim 14 wherein securing the selected medial and lateral bearingscomprises aligning respective engagement structures on the selectedtibial tray with complementary engagement structures formed on themedial and lateral bearings and, further comprising: slidably advancinga locking bar into contact with the respective engagement structures onthe tray and the complementary engagement structures on the medial andlateral bearings.
 17. A knee joint prosthesis assembly comprising: aunitary tibial component having a medial portion that includes a firstengagement structure and a lateral portion that includes a secondengagement structure; a medial bearing having a third engagementstructure formed thereon that selectively engages the first engagementstructure; a lateral bearing separately formed and independent from themedial bearing and having a fourth engagement structure formed thereonthat selectively engages the second engagement structure; and a lockingbar that selectively locates between the tibial component and the medialand lateral bearings, the locking bar cooperating with the first,second, third and fourth engagement structures and securing the medialand lateral bearings to the tibial component.